Directline enhanced auth sample: Bring back to experimental and modernize

[carlosscastro]

The original direcline enhanced authentication sample was deleted but docs link to it so we want to bring it back. However, the sample was outdated and as we bring it back, we'd like to modernize it to use the latest SDK patterns and be consistent with the core SDK samples.

As part of this work, we could consider also improving the sample to use razor for the dotnet consumption example: https://github.com/EricDahlvang/SuperSimpleProxyBot/blob/master/Pages/Index.cshtml

Additionally, consider adding consume the token in a javascript client.

Finally, consider providing samples for non-webchat scenarios, such as when using a directline client or the directline api.

fyi @EricDahlvang